ADAPTER-OIL PUMP 3242717 - Caterpillar

Illustration 1 g00486525
Main relief valve (earlier models)
(1) Inlet passage
(2) Dump valve
(3) Spring
(4) Pilot valve
(5) Spring
(6) Nut
(7) Drain passage
(8) Drain passage
(9) Retainer The main relief valve is in front of all other valves in the implement hydraulic system. The relief valve is a pilot-operated cartridge type valve. The pressure setting of the valve is approximately 27000 kPa (3900 psi). The setting of the relief valve is above all the operating pressures. The relief valve is used as a backup valve. The valve limits any pump pressure surges.Pump oil goes into inlet passage (1), through the orifice in the center of dump valve (2) and into the chamber for spring (3). The pressure of the oil is against pilot valve (4). When the oil pressure is less than the setting of the relief valve, the force of spring (5) keeps the pilot valve closed.When the pressure of the oil gets as high as the setting on the relief valve, pilot valve (4) opens. The oil in the chamber for spring (3) flows around pilot valve (4) and through drain passage (8) to the oil tank. Now, only the force of spring (3) is against dump valve (2) so the dump valve opens. The oil from inlet passage (1) can now flow through drain passage (7) to the oil tank. The pressure of the oil in the system is now limited by the setting of the relief valve.A change in the force of spring (5) will change the pressure setting of the relief valve. Loosen nut (6) and turn retainer (9) clockwise in order to increase the pressure setting. Turn retainer (9) counterclockwise in order to decrease the pressure setting of the relief valve.